The present invention relates to devices having substrates with openings passing through the substrates and conductors in the openings. Some devices of the invention incorporate non-electronically-functioning components. Examples include micro-electro-mechanical systems (MEMS) and other micro-structure-technology (MST) structures.
Integrated circuit fabrication technology has been used to create micro-electro-mechanical and micro-electro-optical structures. Examples of such structures include relays, micropumps, and optical devices for fingerprint recognition. FIG. 1 illustrates one such structure 120 formed on a semiconductor die (xe2x80x9cchipxe2x80x9d) 130. The die contains electronic circuitry (not shown) and interconnect lines (not shown) which couple the structure 120 to contact pads 140. The die has been fabricated in a batch process with other such dies on a semiconductor wafer. After the die was separated from the wafer by dicing, bond wires 150 were bonded to the contact pads 140 and lead frame pins 160. Then the lead frame was encapsulated into a ceramic substrate 170, with pins 160 protruding from the substrate. Another substrate 180 was bonded to substrate 170 to protect the die and the structure 120. If the structure 120 is an optical device (e.g. a mirror or an optical sensor), the substrate 180 is made of a suitable transparent material, e.g. glass.
Improved fabrication techniques and structures suitable for such devices are desirable. It is also desirable to increase the mechanical strength of devices with or without non-electrically functioning components.
Some embodiments of the present invention combine techniques for fabricating micro-electro-mechanical and micro-electro-optical structures with backside contact fabrication technology used for vertical integration and described in PCT publication WO 98/19337 (TruSi Technologies, LLC, May 7, 1998).
The invention is not limited to such embodiments. In some embodiments, a fabrication method comprises:
forming a structure that has one or more substrates, wherein the one or more substrates are either a single substrate or a plurality of substrates bonded together, wherein the structure comprises a non-electronically-functioning component which includes at least a portion of the one or more substrates and/or is attached to the one or more substrates;
wherein the one or more substrates include a first substrate which has: a first side, an opening in the first side, and a conductor in the opening;
wherein the method comprises removing material from the structure so that the conductor becomes exposed on a second side of the first substrate.
In some embodiments, the second side is a backside of the first substrate, and the exposed conductor provides backside contact pads. The front side of the first substrate can be bonded to another substrate or substrates which protect the non-electronically-functioning component during processing, including the processing that exposes the conductor. The component is also protected during dicing. The other substrate or substrates can be transparent as needed in the case of an optical component. The other substrate or substrates can be closely positioned to the component to reduce optical distortion. Also, small system area can be achieved.
In some embodiments, the fabrication method comprises:
forming a structure comprising a first substrate which has: a first side, an opening in the first side, and a conductor in the opening;
removing material from the structure so that the conductor becomes exposed on a second side of the first substrate;
wherein removing of the material comprises removing the material from a first portion of the second side of the first substrate to cause the first portion to be recessed relative to a second portion of the second side of the first substrate.
The resulting structure may or may not have a non-electronically-functioning component. In some embodiments, the first substrate is thicker at the second portion than at the first portion. The thicker second portion improves the mechanical strength of the structure.
Other features and advantages of the invention are described below.